An expanding plug of the generic kind is known from German patent 16 25 394. In this case the thick-walled slotted expanding sleeve is provided with a conical inclined surface widening outwards, thus being frusto-conical, at its plug-in end facing away from the head of the screw. It is followed by a circular cylindrical inner wall section followed by a further conical inclined surface in turn tapering in the direction towards the head of the screw. The inner space of the expanding sleeve is passed through by the screw bolt which engages with a conical expanding body bearing against the inclined surface with an equally inclined conical expanding surface at the plug-in end of the expanding sleeve. A further expanding body is provided, which is associated with the inclined surface of minor diameter. Both expanding bodies are connected with one another by way of a spacing sleeve. The advantage of this expanding plug resides in that it practically expands uniformly over its total length. On the other hand it is very expensive to manufacture. Furthermore, the expanding bodies and the spacing sleeves fall out of the expanding sleeve when the screw is screwed out.
An expanding plug is known from German published patent application 27 11 845 having an expanding body with several expanding surfaces one arranged behind the other in longitudinal direction. The expanding body may be rolled from metal sheet with these expanding surfaces being provided on cams punched out of the wall of the expanding body outwards. Several jaws are arranged around this expanding body and held together by means of gripping rings. These jaws, too, may be punched out of metal sheet, with conically extending cams being provided having inclined surfaces associated with the expanding surfaces. In this case, too, the expanding body is not held between the jaws in such a way that it cannot get lost. Moreover, a disadvantage resides in that upon expansion the gripping rings must either be torn or consist of an elastic material adversely affecting the stability of the plug.
It is generally known to manufacture the expanding sleeves of expanding plugs in one piece from a sheet blank by bending.